Over the last 40 years, a great many IMDs have been clinically implanted in patients to treat cardiac arrhythmias and other disorders including implantable cardioverter/defibrillators (ICDs) and pacemakers having single or dual chamber pacing capabilities, cardiomyostimulators, ischemia treatment devices, and drug delivery devices. Recently developed implantable pacemakers and ICDs have been provided with sophisticated arrhythmia detection and discrimination systems based on heart rate, the morphology and other characteristics of the atrial and ventricular EGM and other characteristics of the EGM. Most of these IMDs employ electrical leads bearing bipolar electrode pairs located adjacent to or in a heart chamber for sensing a near field EGM or having one of the electrodes located on the IMD housing for sensing a far field, unipolar EGM. In either case, the near field or far field EGM signals across the electrode pairs are filtered and amplified in sense amplifiers coupled thereto and then processed for recording the sampled EGM or for deriving sense event signals from the EGM.
In current IMDs providing a therapy for treating a cardiac arrhythmia, the sense event signals and certain aspects of the sampled EGM waveform are utilized to automatically detect a cardiac arrhythmia and to control the delivery of an appropriate therapy in accordance with detection and therapy delivery operating algorithms. In such cardiac IMDs providing pacing or cardioversion/defibrillation therapies, both analog and digital signal processing of the EGM is continuously carried out to sense the P-wave and/or R-wave events and to determine when a cardiac arrhythmia episode occurs. For example, a digital signal processing algorithm is employed to distinguish various atrial and ventricular tachyarrhythmias from one another. When a tachyarrhythmia episode is detected, at least selected EGM signal segments and sense event histogram data or the like are stored on a FIFO basis in internal RAM for telemetry out to an external programmer at a later time. Many of these IMDs are also capable of being operated to sample the EGM and transmit real time EGM data of indefinite length via uplink telemetry transmissions to the external programmer when a real time telemetry session is initiated by the medical care provider using the programmer.
Implantable cardiac monitors have also been developed and clinically implanted that employ the capability of recording cardiac EGM data for subsequent interrogation and uplink telemetry transmission to an external programmer for analysis by a physician. The recorded data is periodically telemetered out to a programmer operated by the medical care provider in an uplink telemetry transmission during a telemetry session initiated by a downlink telemetry transmission and receipt of an interrogation command.
The MEDTRONIC® Reveal™ insertable loop recorder is a form of implantable monitor that is intended to be implanted subcutaneously and has a pair of sense electrodes spaced apart on the device housing that are used to pick up the cardiac far field EGM which in this case is also characterized as a “subcutaneous ECG”. The Reveal™ insertable loop recorder samples and records one or more segment (depending on the programmed operating mode) of such far field EGM or subcutaneous ECG signals when the patient feels the effects of an arrhythmic episode and activates the recording function by applying a magnet over the site of implantation. For example, the storage of a programmable length segment of the EGM can be initiated when the patient feels faint due to a bradycardia or tachycardia or feels the palpitations that accompany certain tachycardias. The memory capacity is limited, and so the segments of such EGM episode data that are stored in memory can be written over with new EGM episode data when the patient triggers storage and the memory is full. The most recently stored segment or segments of episode data is transmitted via an uplink telemetry transmission to an external programmer when a memory interrogation telemetry session is initiated by the physician or medical care provider using the programmer. Aspects of the Reveal™ insertable loop recorder are disclosed in commonly assigned PCT publication WO98/02209, incorporated by reference herein in its entirety.
More complex implantable monitors and pacemaker IPGs of this type but having more electrodes arranged in a planar array on the device housing are disclosed in commonly assigned U.S. Pat. No. 5,331,966, incorporated herein by reference in its entirety. Three electrodes are employed to provide a pair of orthogonal sensed EGM or “subcutaneous ECG” signals at the subcutaneous implantation site. A lead can be employed in a disclosed pacemaker embodiment to locate a bipolar electrode pair in a heart chamber to provide an additional near field EGM sense signal from which the P-wave or R-wave can be sensed (depending on the location of the bipolar electrode pair) and through which pacing pulses can be applied to the atrium or ventricle. Recording of the near field and far field EGM episode data can be invoked automatically by detection of a bradycardia or satisfaction of tachyarrhythmia detection criteria or can be manually commenced by the patient using an external limited function programmer or can be commenced by the physician using a full function programmer.
In all of these IMDs having a cardiac monitoring function, the cardiac EGM is continually sensed and sampled in such monitors and recording of EGM episode data is triggered in a variety of ways. The relatively inexpensive and simple to implant Reveal™ insertable loop recorder has been favorably compared to the “black box” of an aircraft by physicians that have prescribed its implantation and use in a number of patients. Recordings of EGM episode data triggered by the patient using the relatively simple Reveal™ insertable loop recorder have proven to be of great value in diagnosing the causes of symptoms felt by the patients and in prescribing the implantation and programming of more complex therapy delivery IMDs, e.g., multi-programmable physiologic DDDR pacemakers and single and dual chamber ICDs.
A variety of other programmable implantable medical devices such as hemodynamic monitors and other physiological monitors are available. These include both implantable pacemakers and defibrillators as well as subcutaneous monitors, for example as disclosed in U.S. Pat. Nos. 5,331,966, 5,987,352, 6,230,059, 6,236,882, 6,381,493 and 7,035,684, all incorporated by reference herein in their entireties.
Programming commands or data are typically transmitted between an implanted RF telemetry antenna and associated circuitry and an external RF telemetry antenna associated with the external programmer. The transmitted telemetry to the implanted device typically allows the physician to program the operation of the device. In the context of implantable ECG monitors, for example, as discussed in the above cited references, extensive programming options may be available directed to the types of arrhythmias to be detected, the criteria for detecting the arrhythmias and the storage of Data related to the detected arrhythmias. One commercially available subcutaneous monitor of this type is the Reveal AF™ device, available from Medtronic, Inc.
Because memory space is limited in such devices, Prioritization of stored data is desirable so the physician can be sure that the information of highest priority is preferentially stored. Exemplary data prioritization schemes are disclosed in U.S. Pat. Nos. 6,230,059, 6,236,882, 5,944,745, 7,130,678 and 6,589,187, all incorporated herein by reference. Normally, the physician has the option of setting the priorities for data storage by means of the external programmer.
Such devices also typically have arrhythmia detection capabilities which the physician may also set to conform to the patient's condition, by means of activation or deactivation of arrhythmia detection mechanisms and by adjusting particular parameters associated with arrhythmia detection, such as heart rates. Exemplary detection mechanisms for implantable devices are disclosed in U.S. Pat. Nos. 6,236,882, 6,381,493, all incorporated herein by reference.
Because programming of implantable devices can be complex and time consuming, mechanisms have been proposed for simplifying this process. Such mechanisms are sometimes known as “Programming Wizards”. Such mechanisms are disclosed in US Patent Publication Nos. 20110098637 and 20060020292, incorporated herein by reference in their entireties. Using such mechanisms, diagnostic information concerning the patient is entered by the physician and the “wizard” suggests device parameters to be programmed.